Method of mounting lenses



y 6, 1952 A. BUTLER 2,595,760

METHOD OF MOUNTING LENSES Filed Sept. 2, 1949- ALBERT .Bl/TLER.

fi y fwowjd patented May 6,

UNITED: STATES PATENT F F ICE,

2,595,760 MET'iion-oi?MoUNTihdLiiNsss Albert Butler; Toronto, Ontarid, 'CaInada','-=asslgnor to hnperial-Qptical; Company, Ltd. Toronto, Ontario, Canada, a corporation of Canada; Application-September 2, 1949; Serial No; 113,708 3 Claims." (01. 51+2s4 Thislinvention relates toa method of' i'nounting and demounting lenses in a lens :chuck.

Itis customary in the manufaeture ofxophthalmic lenses to grind and polishone side, mount the. le'n's' in sometype ofholding device to expose the; unfinished side, andthen to finish the unfinished or secondside'in the grinding, fining and polishing machines.= To my knowledge, a great number of-types of. chucks or holding devices have been tried'forholding lenses in these machine'swhile the sec'ondside is being finished but the standard type of lenslholder, in whichthe finished side oft'helen'sis embedded and held-in optical pitch or somelother adhesive, is still widely 'used. while the standard type" oflens holder hasbeen preferred in th'epast, it isfar from being a perfect means for holding a lens;

The great disadvantage with the standard type of lenshoIder in which the lens is embedded in optical pitch or the like; is that the lens tends to shift position in the pitch as it is being ground r due to the contraction and expansion of, the pitch; with the result that the len's .isground thinner at one point'o'n its edge than at a diamet= rically-opposed-point on itsedger This 'defectis known as prism;

The lens chucks'of the'prior art of-which I have knowledge that have departed from theprinciple' ofsupporting a lens' 'inopti'cal pitch, to overcome' this and other defects; have :been impractical for a variety of reasons.

I have developed a practical lensuchuck forrlgidly supporting .a lens while its second surface isbeln'gprecislon ground.

It' is' a further object of this invention to provide a method for quickly and efliciently' mountingand demounting lenses on achuck having a rigid mechanical'surface' for the purpose of supporting a lens. 7

With theseand other objects in view, a lens chuck according to my. invention comprises a cupped bodyventilated adjacent its bottom and Figure 1 is a erspecm ve view of a was chuck in the crosssectional Figure 2. It has a central according to the present invention with a-lens" mounted thereonpartly cut away to show the manner in which the'lens is mounted.

Figure 2 is --a crosssectional view of the lens invention; 3 Itwill-be 'seei'f to comprise a cupped body l0" having a projecting "shank" l I centrally" located on the "bo'ttom outside thereof tor the purpose of mounting -it in a grinding, fining or polishing machine;

The construction of the shank His illustrated bore designed toreceive the plug --l2, -the top of which is formed with a conical depression- 13 for coaction with the'polishi'ng machine where a floating relation between the lens 'andthe polishi ng lap is requiredv Themounting- :of lens chucks in lens grinding, fining and polishing inachines; however; is well known and i it; is 'not thought necessary that it should he-expanded" upon atany greaterleng'th "in the 'prese'nt' application.

The edges of 'th'e cupped tddy-|caremacmrleu a lens 14; The lens 14' shown'ln-the drawings' is a cylinder lens and to this-end the edges -of the cupped body I 0 I are accordingly" ground one direction with a cylinder'curv'e l5"equal in= radius to the radius of the base'curve of' the finished plus side of the lens l4 and ground in a dimetion at right angles thereto with-a cylinder curve [6 equal in radius td th'eradius of thel'cross' curve ofthe finished plus side of' the-lensdd':

Ventilation holes I 1 areformed" in the bottom" surface ofthe cupped'bo'dy 10 In ordrtomo'unt a lens in'a chuck according to'my'lnventi'on a paper liner"l8'is placed over the bottom interior surface of the cupped body it. A quantity of'opticallpitch or "other' suitable" adhesive is then placed inthe 'cuptand the edges of' the-cup l9 and" with "its cross curve aligned with the cross curve "I 6 ground "in the edges of the cup. In this connection the opposed sides of the cup are preferably marked as at 15a to indicate the centre of the cylinder base curve l5 formed on the edges of the cup. A corresponding marking is usually found on minus side of the lens for the purpose of demarking the centre of the base curve of the lens. The lens can be quickly aligned on the machined edge of the cupped body of the chuck by aligning the base curve marks on the lens with the base curve marks on the sides of the cup.

After the lens has been caused to abut the machined edge of the cup II! with the cylinder curves of the plus side of the lens aligned with the cylinder curves formed on the edges of the cup, it is clamped into position by means of a suitable clamp I9 and the entire assembly is placed into an oven with the chuck overlying the lens. The oven is heated to a temperature of about 200 F. -for the purpose of melting the optical pitch and causing it to flow over the top of the lens 14 and the interior sides of the cupped body If]. When the pitch has been melted the assembly is withdrawn from the oven and allowed to cool to room temperature with the chuck still overlying the lens. As the pitch hardens it will adhere to the sides of the cupped body 10 and to the plus surface of the lens M to firmly retain the lens against the machined edges of the cupped body ii]. The chuck carrying the lens is then mounted in the various machines used for finishing the minus side of the lens 14.

In order to remove the lens [4 from the chuck according to my invention I place the lens carrying chuck in a cold box and cool it to a temperature of about F. to cause the pitch within the chuck to contract and to release the lens which was formerly held against the cylinder machined edges l and Hi. Just as soon as the lens 14 has been released due to the contraction of the pitch I remove the separated lens and the chuck from the cold box. The procedure can then be repeated by clamping a second lens to the chuck and placing it in the oven again as before to mount another lens in the chuck.

The purpose of the paper liner "3 on the bottom interior of the cupped body I0 is to absorb the strains and stresses caused by expansion and contraction of the pitch. It is well known that when pitch is cooled it contracts considerably, and if no paper liner were provided and the pitch l8 were permitted to come in contact with the bottom interior of the cupped body In the pitch would probably adhere to the bottom of the cupped body It and pull away from the lens surface l4 to release the lens.

The holes [1 formed in the top of the cupped body ID are for the purpose of providing ventilation within the cup as the pitch contracts and expands.

I have described the chuck according to my invention the edges of which are machined to accommodate a specific cylinder lens. It will be apparent that a different chuck will be required for the various size cylinder lenses. It will also be apparent that the edges of the chuck could be machined to accommodate a cylindrical lens surface.

What I claim as my invention is:

1. A method for mounting and demounting lenses on a lens chuck, the said lens chuck having a cupped body with machined edges to abut with the surfaces of lenses applied thereto, the said chuck further having a quantity of pitch that is solid at room temperature within its cupped body, comprising the steps of placing a lens over the machined edges of the said cupped body, clamping said lens over the machined edges of the said cupped body, heating said chuck and lens with said chuck overlying said lens to melt said pitch, cooling said lens chuck and pitch to room temperature while maintaining said chuck above said lens whereby to cause said pitch to solidify against said lens and retain said lens against the edges of said cupped body, said lens at this stage of the process being mounted on said lens holder, cooling said lens and said chuck below room temperature to cause said pitch to contract and release said lens from said chuck, said lens at this stage of the process being demounted from said lens chuck, the foregoing steps being repeated with different lenses on the same chuck and without removing the pitch therefrom.

2. A method for mounting and demounting lenses on a lens chuck, the said lens chuck having a cupped body with machined edges to abut with the surfaces to the lenses applied thereto and a vented bottom, the said chuck further having a quantity of pitch that is solid at room temperature within its cupped body, comprising the steps of placing a lens over the machined edges of the said cupped body, clamping said lens over the machined edges of the said cupped body, heating said chuck and lens with said chuck overlying said lens to melt said pitch, said pitch being in a quantity whereby communication between the atmosphere and the bottom interior of said cupped body is achieved through said vented bottom at this stage of the process, cooling said lens chuck and pitch to room temperature while maintaining said chuck above said lens whereby to cause said pitch to solidify against said lens and retain said lens against the edges of said cupped body, said lens at this stage of the process being mounted on said lens holder, cooling said lens and said chuck below room temperature to cause said chuck, said lens at this stage of the process being demounted from said lens chuck, the foregoing steps being repeated with different lenses on the same chuck and without removing the pitch therefrom.

3. A method for mounting and demounting lenses on a lens chuck, said lens chuck having a cupped body with machined edges to abut with the surfaces of lenses applied thereto and a vented bottom, the said chuck having a paper liner for its bottom interior, the said chuck still further having a quantity of pitch that is solid at room temperature within its cupped body, comprising the steps of placing a lens over the machined edges of the said cupped body, clamping said lens over the machined edges of the said cupped body, heating said chuck and lens with said chuck overlying said lens to melt said pitch, said pitch being in a quantity whereby communication between the atmosphere and the bottom interior of said cupped body is achieved through said vented bottom at this stage of the process, cooling said lens chuck and pitch to room temperature while maintaining said chuck. above said lens whereby to cause said pitch to solidify against said lens and retain said lens at this stage of the process being mounted on said lens holder, cooling said lens and said chuck below room temperature to cause said pitch to contract and release said lens from said chuck, said lens at this stage of the process being demounted from said lens chuck, the foregoing steps being repeated with different lenses on the 6 Name Date H111 Mar. 27, 1934 McClernon Dec. 2, 1941 Bolsey June 27, 1944 Fritzsche Mar. 22, 1949 FOREIGN PATENTS Country Date Germany Mar. 20, 1923 Germany Oct. 13, 1927 OTHER REFERENCES Prism and Lens Making, by F. Twyman, published by Adam Hilger Ltd., London, England,

1942. pp. 64 and 65. 

